Method of selecting a light redirecting film

ABSTRACT

The method of selecting a light redirecting film or optical panel includes the steps of providing a length of film or substrate having a pattern of optical elements that varies, then selecting an area of the film or substrate that has a pattern of the optical elements that best suits a particular application, and removing the selected area from the film or substrate to provide the light redirecting film or optical panel. The pattern may be a repeating pattern that varies at different locations on the film or substrate and may comprise a roll of the film or substrate from which the selected area(s) is removed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.09/909,318, filed Jul. 19, 2001, now U.S. Pat. No. 6,752,202, which is acontinuation-in-part of U.S. patent application Ser. No. 09/256,275,filed Feb. 23, 1999, now U.S. Pat. No. 6,712,481, the entire disclosuresof which are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to light redirecting films and film systems forredirecting light from a light source toward a direction normal to theplane of the films.

BACKGROUND OF THE INVENTION

Light redirecting films are thin transparent or translucent opticalfilms or substrates that redistribute the light passing through thefilms such that the distribution of the light exiting the films isdirected more normal to the surface of the films. Heretofore, lightredirecting films were provided with prismatic grooves, lenticulargrooves, or pyramids on the light exit surface of the films whichchanged the angle of the film/air interface for light rays exiting thefilms and caused the components of the incident light distributiontraveling in a plane perpendicular to the refracting surfaces of thegrooves to be redistributed in a direction more normal to the surface ofthe films. Such light redirecting films are used, for example, withliquid crystal displays, used in laptop computers, word processors,avionic displays, cell phones, PDAs and the like to make the displaysbrighter.

The light entrance surface of the films usually has a transparent ormatte finish depending on the visual appearance desired. A matte finishproduces a softer image but is not as bright due to the additionalscattering and resultant light loss caused by the matte or diffusesurface.

Heretofore, most applications used two grooved film layers rotatedrelative to each other such that the grooves in the respective filmlayers are at 90 degrees relative to each other. The reason for this isthat a grooved light redirecting film will only redistribute, towardsthe direction normal to the film surface, the components of the incidentlight distribution traveling in a plane perpendicular to the refractingsurfaces of the grooves. Therefore, to redirect light toward the normalof the film surface in two dimensions, two grooved film layers rotated90 degrees with respect to each other are needed, one film layer toredirect light traveling in a plane perpendicular to the direction ofits grooves and the other film layer to redirect light traveling in aplane perpendicular to the direction of its grooves.

Attempts have been made in the past to create a single layer lightredirecting film that will redirect components of the incident lightdistribution traveling along two different axes 90 degrees to eachother. One known way of accomplishing this is to provide a single layerfilm with two sets of grooves extending perpendicular to each otherresulting in a pyramid structure which redirects light traveling in bothsuch directions. However, such a film produces a much lower brightnessthan two film layers each with a single groove configuration rotated 90degrees with respect to each other because the area that is removed fromthe first set of grooves by the second set of grooves in a single layerfilm reduces the surface area available to redirect light substantiallyby 50% in each direction of travel.

In addition, heretofore, the grooves of light redirecting films havebeen constructed so that all of the grooves meet the surface of thefilms at the same angle, mostly 45 degrees. This design assumes aconstant, diffuse angular distribution of light from the light source,such as a lambertian source, a backlighting panel using a printing oretching technology to extract light, or a backlighting panel behindheavy diffusers. A light redirecting film where all of the lightredirecting surfaces meet the film at the same angle is not optimizedfor a light source that has a nonuniform directional component to itslight emission at different areas above the source. For example, theaverage angle about which a modern high efficiency edge lit backlight,using grooves or micro-optical surfaces to extract light, changes atdifferent distances from the light source, requiring a different anglebetween the light redirecting surfaces and the plane of the film tooptimally redirect light toward the normal of the film.

There is thus a need for a light redirecting film that can produce asofter image while eliminating the decrease in brightness associatedwith a matte or diffuse finish on the light input side of the film.Also, there is a need for a single layer of film which can redirect aportion of the light traveling in a plane parallel to the refractingsurfaces in a grooved film, that would be brighter than a single layerof film using prismatic or lenticular grooves. In addition, there is aneed for a light redirecting film that can compensate for the differentangular distributions of light that may exist for a particular lightsource at different positions above the source, such as backlights usedto illuminate liquid crystal displays. Also, there is a need for a lightredirecting film system in which the film is matched or tuned to thelight output distribution of a backlight or other light source toreorient or redirect more of the incident light from the backlightwithin a desired viewing angle.

SUMMARY OF THE INVENTION

The present invention relates to light redirecting films and lightredirecting film systems that redistribute more of the light emitted bya backlight or other light source toward a direction more normal to theplane of the films, and to light redirecting films that produce a softerimage without the brightness decrease associated with films that have amatte or diffuse finish on the light entrance surface of the films, forincreased effectiveness.

The light exit surface of the films has a pattern of discrete individualoptical elements of well defined shape for refracting the incident lightdistribution such that the distribution of light exiting the films is ina direction more normal to the surface of the films. These individualoptical elements may be formed by depressions in or projections on theexit surface of the films, and include one or more sloping surfaces forrefracting the incident light toward a direction normal to the exitsurface. These sloping surfaces may for example include a combination ofplanar and curved surfaces that redirect the light within a desiredviewing angle. Also, the curvature of the surfaces, or the ratio of thecurved area to the planar area of the individual optical elements aswell as the perimeter shapes of the curved and planar surfaces may bevaried to tailor the light output distribution of the films, tocustomize the viewing angle of the display device used in conjunctionwith the films. In addition, the curvature of the surfaces, or the ratioof the curved area to the planar area of the individual optical elementsmay be varied to redirect more or less light that is traveling in aplane that would be parallel to the grooves of a prismatic or lenticulargrooved film. Also the size and population of the individual opticalelements, as well as the curvature of the surfaces of the individualoptical elements may be chosen to produce a more or less diffuse outputor to randomize the input light distribution from the light source toproduce a softer more diffuse light output distribution whilemaintaining the output distribution within a specified angular regionabout the direction normal to the films.

The light entrance surface of the films may have an optical coating suchas an antireflective coating, a reflective polarizer, a retardationcoating or a polarizer. Also a matte or diffuse texture may be providedon the light entrance surface depending on the visual appearancedesired. A matte finish produces a softer image but is not as bright.

The individual optical elements on the exit surface of the films may berandomized in such a way as to eliminate any interference with the pixelspacing of a liquid crystal display. This randomization can include thesize, shape, position, depth, orientation, angle or density of theoptical elements. This eliminates the need for diffuser layers to defeatmoiré and similar effects. Also, at least some of the individual opticalelements may be arranged in groupings across the exit surface of thefilms, with at least some of the optical elements in each of thegroupings having a different size or shape characteristic thatcollectively produce an average size or shape characteristic for each ofthe groupings that varies across the films to obtain averagecharacteristic values beyond machining tolerances for any single opticalelement and to defeat moiré and interference effects with the pixelspacing of a liquid crystal display. In addition, at least some of theindividual optical elements may be oriented at different angles relativeto each other for customizing the ability of the films toreorient/redirect light along two different axes.

The angles that the light redirecting surfaces of the individual opticalelements make with the light exit surface of the films may also bevaried across the display area of a liquid crystal display to tailor thelight redirecting function of the films to a light input distributionthat is non-uniform across the surface of the light source.

The individual optical elements of the light redirecting films alsodesirably overlap each other, in a staggered, interlocked and/orintersecting configuration, creating an optical structure with excellentsurface area coverage. Moreover, the individual optical elements may bearranged in groupings with some of the individual optical elementsoriented along one axis and other individual optical elements orientedalong another axis. Also, the orientation of the individual opticalelements in each grouping may vary. Further, the size, shape, positionand/or orientation of the individual optical elements of the lightredirecting films may vary to account for variations in the distributionof light emitted by a light source.

The properties and pattern of the optical elements of light redirectingfilms may also be customized to optimize the light redirecting films fordifferent types of light sources which emit different lightdistributions, for example, one pattern for single bulb laptops, anotherpattern for double bulb flat panel displays, and so on.

Further, light redirecting film systems are provided in which theorientation, size, position and/or shape of the individual opticalelements of the light redirecting films are tailored to the light outputdistribution of a backlight or other light source to reorient orredirect more of the incident light from the backlight within a desiredviewing angle. Also, the backlight may include individual opticaldeformities that collimate light along one axis and the lightredirecting films may include individual optical elements that collimatelight along another axis perpendicular to the one axis.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter more fully described andparticularly pointed out in the claims, the following description andannexed drawings setting forth in detail certain illustrativeembodiments of the invention, these being indicative, however, of butseveral of the various ways in which the principles of the invention maybe employed.

BRIEF DESCRIPTION OF THE DRAWINGS

In the annexed drawings:

FIG. 1 is a schematic side elevation view of one form of lightredirecting film system in accordance with the present invention;

FIG. 2 is an enlarged fragmentary side elevation view of a portion ofthe backlight and light redirecting film system of FIG. 1;

FIGS. 3 and 4 are schematic side elevation views of other forms of lightredirecting film systems of the present invention;

FIGS. 5–20 are schematic perspective or plan views showing differentpatterns of individual optical elements on light redirecting films ofthe present invention;

FIGS. 5 a–5 n are schematic perspective views of different geometricshapes that the individual optical elements on the light redirectingfilms may take;

FIG. 21 is a schematic perspective view of a light redirecting filmhaving optical grooves extending across the film in a curved patternfacing a corner of the film;

FIG. 22 is a top plan view of a light redirecting film having a patternof optical grooves extending across the film facing a midpoint on oneedge of the film that decreases in curvature as the distance from theone edge increases;

FIG. 23 is an end elevation view of the light redirecting film of FIG.22 as seen from the left end thereof;

FIG. 24 is a side elevation view of the light redirecting film of FIG.22;

FIGS. 25 and 26 are enlarged schematic fragmentary plan views of asurface area of a backlight/light emitting panel assembly showingvarious forms of optical deformities formed on or in a surface of thebacklight;

FIGS. 27 and 28 are enlarged longitudinal sections through one of theoptical deformities of FIGS. 25 and 26, respectively;

FIGS. 29 and 30 are enlarged schematic longitudinal sections throughother forms of optical deformities formed on or in a surface of abacklight;

FIGS. 31–39 are enlarged schematic perspective views of backlightsurface areas containing various patterns of individual opticaldeformities of other well defined shapes;

FIG. 40 is an enlarged schematic longitudinal section through anotherform of optical deformity formed on or in a surface of a backlight;

FIGS. 41 and 42 are enlarged schematic top plan views of backlightsurface areas containing optical deformities similar in shape to thoseshown in FIGS. 37 and 38 arranged in a plurality of straight rows alongthe length and width of the surface areas;

FIGS. 43 and 44 are enlarged schematic top plan views of backlightsurface areas containing optical deformities also similar in shape tothose shown in FIGS. 37 and 38 arranged in staggered rows along thelength of the surface areas;

FIGS. 45 and 46 are enlarged schematic top plan views of backlightsurface areas containing a random or variable pattern of different sizedoptical deformities on the surface areas;

FIG. 47 is an enlarged schematic perspective view of a backlight surfacearea showing optical deformities increasing in size as the distance ofthe deformities from the light input surface increases or intensity ofthe light increases along the length of the surface area;

FIGS. 48 and 49 are schematic perspective views showing differentangular orientations of the optical deformities along the length andwidth of a backlight surface area; and

FIGS. 50 and 51 are enlarged perspective views schematically showing howexemplary light rays emitted from a focused light source are reflectedor refracted by different individual optical deformities of well definedshapes of a backlight surface area.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 schematically show one form of light redirecting filmsystem 1 in accordance with this invention including a light redirectingfilm 2 that redistributes more of the light emitted by a backlight BL orother light source toward a direction more normal to the surface of thefilm. Film 2 may be used to redistribute light within a desired viewingangle from almost any light source for lighting, for example, a displaysuch as a liquid crystal display, used in laptop computers, wordprocessors, avionic displays, cell phones, PDAs and the like, to makethe displays brighter. The liquid crystal display can be any typeincluding a transmissive liquid crystal display D as schematically shownin FIGS. 1 and 2, a reflective liquid crystal display D^(I) asschematically shown in FIG. 3 and a transflective liquid crystal displayD^(II) as schematically shown in FIG. 4.

The reflective liquid crystal display D′ shown in FIG. 3 includes a backreflector 42 adjacent the back side for reflecting ambient lightentering the display back out the display to increase the brightness ofthe display. The light redirecting film 2 of the present invention isplaced adjacent the top of the reflective liquid crystal display toredirect ambient light (or light from a front light) into the displaytoward a direction more normal to the plane of the film for reflectionback out by the back reflector within a desired viewing angle toincrease the brightness of the display. Light redirecting film 2 may beattached to, laminated to or otherwise held in place against the top ofthe liquid crystal display.

The transflective liquid crystal display D^(II) shown in FIG. 4 includesa transreflector T placed between the display and a backlight BL forreflecting ambient light entering the front of the display back out thedisplay to increase the brightness of the display in a lightedenvironment, and for transmitting light from the backlight through thetransreflector and out the display to illuminate the display in a darkenvironment. In this embodiment the light redirecting film 2 may eitherbe placed adjacent the top of the display or adjacent the bottom of thedisplay or both as schematically shown in FIG. 4 for redirecting orredistributing ambient light and/or light from the backlight more normalto the plane of the film to make the light ray output distribution moreacceptable to travel through the display to increase the brightness ofthe display.

Light redirecting film 2 comprises a thin transparent film or substrate8 having a pattern of discrete individual optical elements 5 of welldefined shape on the light exit surface 6 of the film for refracting theincident light distribution such that the distribution of the lightexiting the film is in a direction more normal to the surface of thefilm.

Each of the individual optical elements 5 has a width and length manytimes smaller than the width and length of the film, and may be formedby depressions in or projections on the exit surface of the film. Theseindividual optical elements 5 include at least one sloping surface forrefracting the incident light toward the direction normal to the lightexit surface. FIG. 5 shows one pattern of individual optical elements 5on a film 2. These optical elements may take many different shapes. Forexample, FIG. 5 a shows one of the optical elements 5 of FIG. 5 which isa non-prismatic optical element having a total of two surfaces 10, 12,both of which are sloping. One of the surfaces 10 shown in FIG. 5 a isplanar or flat whereas the other surface 12 is curved. Moreover, bothsurfaces 10, 12 intersect each other and also intersect the surface ofthe film. Alternatively, both surfaces 10′, 12′ of the individualoptical elements 5′ may be curved as schematically shown in FIG. 5 b.

Alternatively, the optical elements may each have only one surface thatis curved and sloping and intersects the film. FIG. 5 c shows one suchoptical element 5 ^(II) in the shape of a cone 13, whereas FIG. 5 dshows another such optical element 5 ^(III) having a semispherical ordome shape 14. Also, such optical elements may have more than onesloping surface intersecting the film.

FIG. 5 e shows an optical element 5 ^(IV) having a total of threesurfaces, all of which intersect the film and intersect each other. Twoof the surfaces 15 and 16 are curved, whereas the third surface 17 isplanar.

FIG. 5 f shows an optical element 5 ^(V) in the shape of a pyramid 18with four triangular shaped sides 19 that intersect each other andintersect the film. The sides 19 of the pyramid 18 may all be of thesame size and shape as shown in FIG. 5 f, or the sides 19 ^(I) of thepyramid 18 ^(I) may be stretched so the sides of the optical element 5^(VI) have different perimeter shapes as shown in FIG. 5 g. Also, theoptical elements may have any number of planar sloping sides. FIG. 5 hshows an optical element 5 ^(VII) with four planar sloping sides 20,whereas FIG. 5 i shows an optical element 5 ^(VIII) with eight planarsloping sides 20 ^(I).

The individual optical elements may also have more than one curved andmore than one planar sloping surface, all intersecting the film. FIG. 5j shows an optical element 5 ^(IX) having a pair of intersectingoppositely sloping planar sides 22 and oppositely rounded or curved endsor sides 23. Further, the sloping planar sides 22 ^(I) and 22 ^(II) andcurved ends or sides 23 ^(I) and 23 ^(II) of optical elements 5 ^(x) and5 ^(Xi) may have different angled slopes as shown in FIGS. 5 k and 51.Moreover, the optical elements may have at least one curved surface thatdoes not intersect the film. One such optical element 5 ^(XII) is shownin FIG. 5 m which includes a pair of oppositely sloping planar sides 22^(III) and oppositely rounded or curved ends or sides 23 ^(III) and arounded or curved top 24 intersecting the oppositely sloping sides andoppositely rounded ends. Further, the optical elements 5 ^(XIII) may becurved along their length as shown in FIG. 5 n.

Providing the individual optical elements with a combination of planarand curved surfaces redirects or redistributes a larger viewing areathan is possible with a grooved film. Also, the curvature of thesurfaces, or the ratio of the curved area to the planar area of theindividual optical elements may be varied to tailor the light outputdistribution of the film to customize the viewing area of a displaydevice used in conjunction with the film.

The light entrance surface 7 of the film 2 may have an optical coating25 (see FIG. 2) such as an antireflective coating, a reflectivepolarizer, a retardation coating or a polarizer. Also, a matte ordiffuse texture may be provided on the light entrance surface 7depending on the visual appearance desired. A matte finish produces asofter image but is not as bright. The combination of planar and curvedsurfaces of the individual optical elements of the present invention maybe configured to redirect some of the light rays impinging thereon indifferent directions to produce a softer image without the need for anadditional diffuser or matte finish on the entrance surface of the film.

The individual optical elements of the light redirecting film alsodesirably overlap each other in a staggered, interlocked and/orintersecting configuration, creating an optical structure with excellentsurface area coverage. FIGS. 6, 7, 13 and 15, for example, show opticalelements 5 ^(XIV), 5 ^(XV), 5 ^(XVI), and 5 ^(XVII) of light redirectingfilms 2 ^(I), 2 ^(II), 2 ^(IV) and 2 ^(IV) staggered with respect toeach other; FIGS. 8–10 show the optical elements 5 ^(XVIII), 5 ^(XIX)and 5 ^(XX) of light redirecting films 2 ^(V), 2 ^(VI) and 2 ^(VII)intersecting each other; and FIGS. 11 and 12 show the optical elementsintersecting 5 ^(XXI) and 5 ^(XXII) of light redirecting films 2 ^(VIII)and 2 ^(IX) interlocking each other.

Moreover, the slope angle, density, position, orientation, height ordepth, shape, and/or size of the optical elements of the lightredirecting film may be matched or tuned to the particular light outputdistribution of a backlight BL or other light source to account forvariations in the distribution of light emitted by the backlight inorder to redistribute more of the light emitted by the backlight withina desired viewing angle. For example, the angle that the slopingsurfaces (e.g., surfaces 10, 12) of the optical elements 5 make with thesurface of the light redirecting film 2 may be varied as the distancefrom the backlight BL from a light source 26 increases to account forthe way the backlight emits light rays R at different angles as thedistance from the light source increases as schematically shown in FIG.2. Also, the backlight BL itself may be designed to emit more of thelight rays at lower angles to increase the amount of light emitted bythe backlight and rely on the light redirecting film to redistributemore of the emitted light within a desired viewing angle. In this waythe individual optical elements of the light redirecting film may beselected to work in conjunction with the optical deformations of thebacklight to produce an optimized output light ray angle distributionfrom the system.

FIGS. 2, 5 and 9 show different patterns of individual optical elementsall of the same height or depth, whereas FIGS. 7, 8, 10, 13 and 14 showdifferent patterns of individual optical elements of different shapes,sizes and height or depth. The individual optical elements 5 ^(XXIII) ofthe light redirecting film 2 ^(X) of FIG. 14 are also shown arranged inalternating rows along the width or length of the film.

The individual optical elements 5 ^(XXV) and 5 ^(XXVI) may also berandomized on the film 2 ^(XI) and 2 ^(XII) as schematically shown inFIGS. 16 and 17 in such a way as to eliminate any interference with thepixel spacing of a liquid crystal display. This eliminates the need foroptical diffuser layers 30 shown in FIGS. 1 and 2 to defeat moiré andsimilar effects. Moreover, at least some of the individual opticalelements may be arranged in groupings 32, 32 ^(I) and 32 ^(II) acrossthe film, with at least some of the optical elements in each groupinghaving a different size or shape characteristic that collectivelyproduce an average size or shape characteristic for each of thegroupings that varies across the film as schematically shown in FIGS. 7,13 and 15 to obtain characteristic values beyond machining tolerances todefeat moiré and interference effects with the liquid crystal displaypixel spacing. For example, at least some of the optical elements ineach grouping may have a different depth or height that collectivelyproduce an average depth or height characteristic for each grouping thatvaries across the film. Also, at least some of the optical elements ineach grouping may have a different slope angle that collectively producean average slope angle for each grouping that varies across the film.Further, at least one sloping surface of the individual optical elementsin each grouping may have a different width or length that collectivelyproduce an average width or length characteristic in each grouping thatvaries across the film.

Where the individual optical elements include a combination of planarand curved surfaces, for example planar and curved surfaces 10 ^(II), 12^(II), 10 ^(III), 12 ^(III) and 10 ^(IV), 12 ^(IV) as shown in FIGS. 7,13 and 15, respectively, the curvature of the curved surfaces, or theratio of the curved area to the planar area of the individual opticalelements as well as the perimeter shapes of the curved and planarsurfaces may be varied to tailor the light output distribution of thefilm. In addition, the curvature of the curved surfaces, or the ratio ofthe curved area to the planar area of the individual optical elementsmay be varied to redirect more or less light that is traveling in aplane that would be parallel to the grooves of a prismatic or lenticulargrooved film, partially or completely replacing the need for a secondlayer of light redirecting film. Also, at least some of the individualoptical elements may be oriented at different angles relative to eachother as schematically shown in FIGS. 13 and 16 to redistribute more ofthe light emitted by a light source along two different axes in adirection more normal to the surface of the film, partially orcompletely replacing the need for a second layer of light redirectingfilm. However, it will be appreciated that two layers of such lightredirecting film each having the same or different patterns ofindividual optical elements thereon may be placed between a light sourceand viewing area with the layers rotated 90 degrees (or other anglesgreater than 0 degrees and less than 90 degrees) with respect to eachother so that the individual optical elements on the respective filmlayers redistribute more of the light emitted by a light sourcetraveling in different planar directions in a direction more normal tothe surface of the respective films.

Also, the light redirecting film 2 ^(IV) may have a pattern of opticalelements 5 ^(XVII) that varies at different locations on the film asschematically shown in FIG. 15 to redistribute the light ray outputdistribution from different locations of a backlight or other lightsource to redistribute the light ray output distribution from thedifferent locations toward a direction normal to the film.

Further, the properties and pattern of the optical elements of the lightredirecting film may be customized to optimize the light redirectingfilm for different types of light sources which emit different lightdistributions, for example, one pattern for single bulb laptops, anotherpattern for double bulb flat panel displays, and so on.

FIG. 17 shows the optical elements 5 ^(XXVI) arranged in a radialpattern from the outside edges of the film 2 ^(XII) toward the center toredistribute the light ray output distribution of a backlight BL thatreceives light from cold cathode fluorescent lamp 26 ^(I) along all fourside edges of the backlight.

FIG. 18 shows the optical elements 5 ^(XXVII) arranged in a pattern ofangled groupings 32 ^(III) across the film 2 that are tailored toredistribute the light ray output distribution of a backlight BL thatreceives light from one cold cathode fluorescent lamp 26 ^(I) or aplurality of light emitting diodes 26 ^(II) along one input edge of thebacklight.

FIG. 19 shows the optical elements 5 ^(XXVIII) arranged in a radial typepattern facing a corner of the film 2 ^(XIV) to redistribute the lightray output distribution of a backlight BL that is corner lit by a lightemitting diode 26 ^(II). FIG. 20 shows the optical elements 5 ^(XXIX)arranged in a radial type pattern facing a midpoint on one input edge ofthe film 2 ^(XV) to redistribute the light ray output distribution of abacklight BL that is lighted at a midpoint of one input edge of thebacklight by a single light emitting diode 26 ^(II).

FIG. 21 shows a light redirecting film 2 ^(XVI) having optical grooves35 extending across the film in a curved pattern facing a corner of thefilm to redistribute the light ray output distribution of a backlight BLthat is corner lit by a light emitting diode 26 ^(II), whereas FIGS.22–24 show a light redirecting film 2 ^(XVII) having a pattern ofoptical grooves 35 ^(I) extending across the film facing a midpointalong one edge of the film that decreases in curvature as the distancefrom the one edge increases to redistribute the light ray outputdistribution of a backlight BL that is edge lit by a light emittingdiode 26 ^(II) at a midpoint of one input edge of the backlight.

Where the light redirecting film has a pattern 40 of optical elements 5thereon that varies along the length of the film, a roll 41 of the filmmay be provided having a repeating pattern of optical elements thereonas schematically shown in FIG. 15 to permit a selected area of thepattern that best suits a particular application to be die cut from theroll of film.

The backlight BL may be substantially flat, or curved, or may be asingle layer or multi-layers, and may have different thicknesses andshapes as desired. Moreover, the backlight may be flexible or rigid, andbe made of a variety of compounds. Further, the backlight may be hollow,filled with liquid, air, or be solid, and may have holes or ridges.

Also, the light source 26 may be of any suitable type including, forexample, an arc lamp, an incandescent bulb which may also be colored,filtered or painted, a lens end bulb, a line light, a halogen lamp, alight emitting diode (LED), a chip from an LED, a neon bulb, a coldcathode fluorescent lamp, a fiber optic light pipe transmitting from aremote source, a laser or laser diode, or any other suitable lightsource. Additionally, the light source 26 may be a multiple colored LED,or a combination of multiple colored radiation sources in order toprovide a desired colored or white light output distribution. Forexample, a plurality of colored lights such as LEDs of different colors(e.g., red, blue, green) or a single LED with multiple color chips maybe employed to create white light or any other colored light outputdistribution by varying the intensities of each individual coloredlight.

A pattern of optical deformities may be provided on one or both sides ofthe backlight BL or on one or more selected areas on one or both sidesof the backlight as desired. As used herein, the term opticaldeformities means any change in the shape or geometry of a surfaceand/or coating or surface treatment that causes a portion of the lightto be emitted from the backlight. These deformities can be produced in avariety of manners, for example, by providing a painted pattern, anetched pattern, machined pattern, a printed pattern, a hot stamppattern, or a molded pattern or the like on selected areas of thebacklight. An ink or print pattern may be applied for example by padprinting, silk printing, inkjet, heat transfer film process or the like.The deformities may also be printed on a sheet or film which is used toapply the deformities to the backlight. This sheet or film may become apermanent part of the backlight for example by attaching or otherwisepositioning the sheet or film against one or both sides of the backlightin order to produce a desired effect.

By varying the density, opaqueness or translucence, shape, depth, color,area, index of refraction or type of deformities on or in an area orareas of the backlight, the light output of the backlight can becontrolled. The deformities may be used to control the percent of lightoutput from a light emitting area of the backlight. For example, lessand/or smaller size deformities may be placed on surface areas whereless light output is wanted. Conversely, a greater percentage of and/orlarger deformities may be placed on surface areas of the backlight wheregreater light output is desired.

Varying the percentages and/or size of deformities in different areas ofthe backlight is necessary in order to provide a substantially uniformlight output distribution. For example, the amount of light travelingthrough the backlight will ordinarily be greater in areas closer to thelight source than in other areas further removed from the light source.A pattern of deformities may be used to adjust for the light varianceswithin the backlight, for example, by providing a denser concentrationof deformities with increased distance from the light source therebyresulting in a more uniform light output distribution from thebacklight.

The deformities may also be used to control the output ray angledistribution from the backlight to suit a particular application. Forexample, if the backlight is used to backlight a liquid crystal display,the light output will be more efficient if the deformities (or a lightredirecting film is used in combination with the backlight) direct thelight rays emitted by the backlight at predetermined ray angles suchthat they will pass through the liquid crystal display with low loss.Additionally, the pattern of optical deformities may be used to adjustfor light output variances attributed to light extractions of thebacklight. The pattern of optical deformities may be printed on thebacklight surface areas utilizing a wide spectrum of paints, inks,coatings, epoxies or the like, ranging from glossy to opaque or both,and may employ half-tone separation techniques to vary the deformitycoverage. Moreover, the pattern of optical deformities may be multiplelayers or vary in index of refraction.

Print patterns of optical deformities may vary in shapes such as dots,squares, diamonds, ellipses, stars, random shapes, and the like. Also,print patterns of sixty lines per inch or finer are desirably employed.This makes the deformities or shapes in the print patterns nearlyinvisible to the human eye in a particular application, therebyeliminating the detection of gradient or banding lines that are commonto light extracting patterns utilizing larger elements. Additionally,the deformities may vary in shape and/or size along the length and/orwidth of the backlight. Also, a random placement pattern of thedeformities may be utilized throughout the length and/or width of thebacklight. The deformities may have shapes or a pattern with no specificangles to reduce moiré or other interference effects. Examples ofmethods to create these random patterns are printing a pattern of shapesusing stochastic print pattern techniques, frequency modulated half tonepatterns, or random dot half tones. Moreover, the deformities may becolored in order to effect color correction in the backlight. The colorof the deformities may also vary throughout the backlight, for example,to provide different colors for the same or different light outputareas.

In addition to or in lieu of the patterns of optical deformities, otheroptical deformities including prismatic or lenticular grooves or crossgrooves, or depressions or raised surfaces of various shapes using morecomplex shapes in a mold pattern may be molded, etched, stamped,thermoformed, hot stamped or the like into or on one or more surfaceareas of the backlight. The prismatic or lenticular surfaces,depressions or raised surfaces will cause a portion of the light rayscontacted thereby to be emitted from the backlight. Also, the angles ofthe prisms, depressions or other surfaces may be varied to direct thelight in different directions to produce a desired light outputdistribution or effect. Moreover, the reflective or refractive surfacesmay have shapes or a pattern with no specific angles to reduce moiré orother interference effects.

A back reflector 42 may be attached or positioned against one side ofthe backlight BL as schematically shown in FIGS. 1 and 2 in order toimprove light output efficiency of the backlight by reflecting the lightemitted from that side back through the backlight for emission throughthe opposite side. Additionally, a pattern of optical deformities 50 maybe provided on one or both sides of the backlight as schematically shownin FIGS. 1 and 2 in order to change the path of the light so that theinternal critical angle is exceeded and a portion of the light isemitted from one or both sides of the backlight.

FIGS. 25–28 show optical deformities 50 ^(I), 50 ^(II) which may eitherbe individual projections 51 on the respective backlight surface areas52 or individual depressions 53 in such surface areas 52 ^(I) of abacklight BI^(I), BL^(II). In either case, each of these opticaldeformities has a well defined shape including a reflective orrefractive surface 54, 54 ^(I) (hereafter sometimes collectivelyreferred to as a reflective/refractive surface) that intersects therespective backlight surface area 52, 52 ^(I) at one edge 55, 55 ^(I)and has a uniform slope throughout its length for more preciselycontrolling the emission of light by each of the deformities. Along aperipheral edge portion 56, 56 ^(I) of each reflective/refractivesurface 54, 54 ^(I) is an end wall 57, 57 ^(I) of each deformity thatintersects the respective panel surface area 52, 52 ^(I) at a greaterincluded angle I, I^(I) than the included angle I^(II), I^(III) betweenthe reflective/refractive surfaces 54, 54 ^(I) and the panel surfacearea 52, 52 ^(I) (see FIGS. 27 and 28) to minimize the projected surfacearea of the end walls on the panel surface area. This allows moredeformities to be placed on or in the panel surface areas than wouldotherwise be possible if the projected surface areas of the end walls57, 57 ^(I) were substantially the same as or greater than the projectedsurface areas of the reflective/refractive surfaces 54, 54 ^(I).

In FIGS. 25 and 26 the peripheral edge portions 56, 56 ^(I) of thereflective/refractive surfaces 54, 54 ^(I) and associated end walls 57,57 ^(I) are curved in the transverse direction. Also in FIGS. 27 and 28the end walls 57, 57 ^(I) of the deformities are shown extendingsubstantially perpendicular to the reflective/refractive surfaces 54, 54^(I) of the deformities. Alternatively, such end walls may extendsubstantially perpendicular to the panel surface areas 52, 52 ^(I) asschematically shown in FIGS. 29 and 30. This virtually eliminates anyprojected surface area of the end walls on the panel surface areaswhereby the density of the deformities on the panel surface areas may beeven further increased.

The optical deformities may also be of other well defined shapes toobtain a desired light output distribution from a panel surface area.FIG. 31 shows individual light extracting deformities 58 on a panelsurface area 52 ^(III) each including a generally planar, rectangularreflective/refractive surface 59 and associated end wall 60 of a uniformslope throughout their length and width and generally planar side walls61. Alternatively, the deformities 58 ^(I) may have rounded or curvedside walls 62 on a panel surface area 52 ^(IV) as schematically shown inFIG. 32.

FIG. 33 shows individual light extracting deformities 63 on a panelsurface area 52 ^(V) each including a planar, sloping triangular shapedreflective/refractive surface 64 and associated planar, generallytriangularly shaped side walls or end walls 65. FIG. 34 shows individuallight extracting deformities 66 on a panel surface area 52 ^(VI) eachincluding a planar sloping reflective/refractive surface 67 havingangled peripheral edge portions 68 and associated angled end and sidewalls 69 and 70.

FIG. 35 shows individual light extracting deformities 71 on a panelsurface area 52 ^(VII) which are generally conically shaped, whereasFIG. 36 shows individual light extracting deformities 72 on a panelsurface area 52 ^(VIII) each including a rounded reflective/refractivesurface 73 and rounded end walls 74 and rounded or curved side walls 75all blended together. These additional surfaces will reflect or refractother light rays impinging thereon in different directions to spreadlight across the backlight/panel member BL to provide a more uniformdistribution of light emitted from the panel member.

Regardless of the particular shape of the reflective/refractive surfacesand end and side walls of the individual deformities, such deformitiesmay also include planar surfaces intersecting the reflective/refractivesurfaces and end and/or side walls in parallel spaced relation to thepanel surface areas 52. FIGS. 37–39 show deformities 76, 77 and 78 inthe form of individual projections on a panel surface area 52 ^(IX), 52^(X), 52 ^(XI) having representative shapes similar to those shown inFIGS. 31, 32 and 35, respectively, except that each deformity isintersected by a planar surface 79, 79 I, 79 ^(II) in parallel spacedrelation to the panel surface area. In like manner, FIG. 40 shows one ofa multitude of deformities 80 in the form of individual depressions 81in a panel surface area 52 ^(XII) each intersected by a planar surface79 ^(III) in parallel spaced relation to the general planar surface ofthe panel surface area. Any light rays that impinge on such planarsurfaces at internal angles less than the critical angle for emission oflight from the panel surface area will be internally reflected by theplanar surfaces, whereas any light rays impinging on such planarsurfaces at internal angles greater than the critical angle will beemitted by the planar surfaces with minimal optical discontinuities, asschematically shown in FIG. 40.

Where the deformities are projections on the panel surface area, thereflective/refractive surfaces extend at an angle away from the panel ina direction generally opposite to that in which the light rays from thelight source 26 travel through the panel as schematically shown in FIGS.27 and 29. Where the deformities are depressions in the panel surfacearea, the reflective/refractive surfaces extend at an angle into thepanel in the same general direction in which the light rays from thelight source 26 travel through the panel member as schematically shownin FIGS. 28 and 30.

Regardless of whether the deformities are projections or depressions onor in the panel surface areas, the slopes of the lightreflective/refractive surfaces of the deformities may be varied to causethe light rays impinging thereon to be either refracted out of the lightemitting panel or reflected back through the panel and emitted out theopposite side of the panel which may be etched to diffuse the lightemitted therefrom or covered by a light redirecting film to produce adesired effect. Also, the pattern of optical deformities on the panelsurface area may be uniform or variable as desired to obtain a desiredlight output distribution from the panel surface areas. FIGS. 41 and 42show deformities 76 ^(I) and 77 ^(I) similar in shape to those shown inFIGS. 37 and 38 arranged in a plurality of generally straight uniformlyspaced apart rows along the length and width of a panel surface area 52^(XIII), 52 ^(XIV), whereas FIGS. 43 and 44 show such deformities 76^(II) and 77 ^(II) arranged in staggered rows that overlap each otheralong the length of a panel surface area 52 ^(XV), 52 ^(XVI).

Also, the size, including the width, length and depth or height as wellas the angular orientation and position of the optical deformities mayvary along the length and/or width of any given panel surface area toobtain a desired light output distribution from the panel surface area.FIGS. 45 and 46 show a random or variable pattern of different sizedeformities 58 ^(II), 58 ^(III) similar in shape to those shown in FIGS.31 and 32, respectively, arranged in staggered rows on a panel surfacearea 52 ^(XVII), 52 ^(XVIII), whereas FIG. 47 shows deformities 77^(III) similar in shape to those shown in FIG. 38 increasing in size asthe distance of the deformities from the light source increases orintensity of the light decreases along the length and/or width of thepanel surface area 52 ^(XIX). The deformities are shown in FIGS. 45 and46 arranged in clusters 82, 82 ^(I) across the panel surface, with atleast some of the deformities in each cluster having a different size orshape characteristic that collectively produce an average size or shapecharacteristic for each of the clusters that varies across the panelsurface. For example, at least some of the deformities in each of theclusters may have a different depth or height or different slope ororientation that collectively produce an average depth or heightcharacteristic or average slope or orientation of the sloping surfacethat varies across the panel surface. Likewise at least some of thedeformities in each of the clusters may have a different width or lengththat collectively produce an average width or length characteristic thatvaries across the panel surface. This allows one to obtain a desiredsize or shape characteristic beyond machinery tolerances, and alsodefeats moiré and interference effects.

FIGS. 48 and 49 schematically show different angular orientations ofoptical deformities 85, 85 ^(I) of any desired shape along the lengthand width of a panel surface area 52 ^(XX), 52 ^(XXI) of a lightemitting panel assembly backlight. In FIG. 48 the deformities arearranged in straight rows 86 along the length of the panel surface areabut the deformities in each of the rows are oriented to face the lightsource 26 so that all of the deformities are substantially in line withthe light rays being emitted from the light source. In FIG. 49 thedeformities 85 ^(I) are also oriented to face the light source 26similar to FIG. 48. In addition, the rows 87 of deformities in FIG. 49are in substantial radial alignment with the light source 26.

FIGS. 50 and 51 schematically show how exemplary light rays 90, 90 ^(I)emitted from a focused light source 26 insert molded or cast within alight transition area 91, 91 ^(I) of a light emitting panel assemblybacklight BL^(III), BL^(IV) in accordance with this invention arereflected during their travel through the light emitting panel member92, 92 ^(I) until they impinge upon individual light extractingdeformities 50 ^(III), 77 ^(IV) of well defined shapes on or in a panelsurface area 52 ^(XXII), 52 ^(XXIII) causing more of the light rays tobe reflected or refracted out of one side 93, 93 ^(I) of the panelmember than the other side 94, 94 ^(I). In FIG. 50 the exemplary lightrays 90 are shown being reflected by the reflective/refractive surfaces54 ^(III) of the deformities 50 ^(III) in the same general direction outthrough the same side 93 of the panel member, whereas in FIG. 51 thelight rays 90 ^(I) are shown being scattered in different directionswithin the panel member 92 ^(I) by the rounded side walls 62 ^(I) of thedeformities 77 ^(IV) before the light rays are reflected/refracted outof the same side 93 ^(I) of the panel member. Such a pattern ofindividual light extracting deformities of well defined shapes inaccordance with the present invention can cause 60 to 70% or more of thelight received through the input edge 95 ^(I) of the panel member to beemitted from the same side of the panel member.

From the foregoing, it will be apparent that the light redirecting filmsof the present invention redistribute more of the light emitted by abacklight or other light source toward a direction more normal to theplane of the films. Also, the light redirecting films and backlights ofthe present invention may be tailored or tuned to each other to providea system in which the individual optical elements of the lightredirecting films work in conjunction with the optical deformities ofthe backlights to produce an optimized output light ray angledistribution from the system.

Although the invention has been shown and described with respect tocertain embodiments, it is obvious that equivalent alterations andmodifications will occur to others skilled in the art upon the readingand understanding of the specification. In particular, with regard tothe various functions performed by the above described components, theterms (including any reference to a “means”) used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed component which performs thefunction in the herein illustrated exemplary embodiments of theinvention. In addition, while a particular feature of the invention mayhave been disclosed with respect to only one embodiment, such featuremay be combined with one or more other features of other embodiments asmay be desired and advantageous for any given or particular application.

1. A method of selecting a light redirecting film for a particularapplication comprising the steps of providing a length of film having apattern of optical elements on or in the film that varies, selecting anarea of the pattern that best suits a particular application, andremoving the selected area from the film to provide the lightredirecting film, the selected area having substantially less than a100% of the total area of the pattern.
 2. The method of claim 1 whereinthe pattern varies along the length of the film.
 3. The method of claim1 wherein the pattern varies along the width of the film.
 4. The methodof claim 1 wherein the pattern varies along the length and width of thefilm.
 5. The method of claim 1 wherein the length of the film comprisesa roll of the film from which the selected area is removed.
 6. Themethod of claim 1 wherein the selected area is die cut from the lengthof the film.
 7. The method of claim 1 wherein the pattern is a repeatingpattern on the film.
 8. The method of claim 7 wherein the length of thefilm comprises a roll of the film from which the selected area isremoved.
 9. The method of claim 8 wherein the selected area is die cutfrom the roll of the film.
 10. A method of selecting a light redirectingfilm for a particular application comprising the steps of providing alength of film having a pattern of individual optical elements of welldefined shape on or in the film that varies, the optical elements beingquite small in relation to a width and length of the film, selecting anarea of the film that has a pattern of the optical elements that bestsuits a particular application, and removing the selected area from thefilm to provide the light redirecting film, the selected area havingsubstantially less than a 100% of the total area of the pattern.
 11. Themethod of claim 10 wherein the pattern is a repeating pattern.
 12. Themethod of claim 10 wherein the pattern varies at different locations onthe film.
 13. The method of claim 10 wherein at least some of theoptical elements overlap, intersect or interlock each other.
 14. Themethod of claim 10 wherein at least some of the optical elements havedifferent shapes.
 15. The method of claim 10 wherein at least some ofthe optical elements have a different beam profile at differentlocations on the film.
 16. The method of claim 10 wherein at least someof the optical elements are randomly distributed on the film.
 17. Themethod of claim 10 wherein at least some of the optical elements areoriented at different angles on the film.
 18. The method of claim 10wherein at least some of the optical elements vary in at least one ofthe following characteristics: slope angle, density, position,orientation, height or depth, shape, and size.
 19. The method of claim10 wherein at least some of the optical elements are arranged ingroupings across the film, with at least some of the optical elements inat least some of the groupings having a different size or shapecharacteristic that collectively produce an average size or shapecharacteristic for each of the groupings that varies across the film.20. A method of selecting an optical panel for a particular applicationcomprising the steps of providing a length of substrate having a patternof optical elements on or in the substrate that varies, selecting anarea of the pattern that best suits a particular application, andremoving the selected area from the substrate to provide the opticalpanel, the selected area having substantially less than a 100% of thetotal area of the pattern.
 21. The method of claim 20 wherein thepattern varies along the length of the substrate.
 22. The method ofclaim 20 wherein the pattern varies along the width of the substrate.23. The method of claim 20 wherein the pattern varies along the lengthand width of the substrate.
 24. The pattern of claim 20 wherein thelength of the substrate comprises a roll of the substrate from which theselected area is removed.
 25. The method of claim 20 wherein theselected area is die cut from the length of the substrate.
 26. Themethod of claim 20 wherein the optical panel is a backlight.
 27. Themethod of claim 20 wherein the pattern is a repeating pattern on thesubstrate.
 28. The method of claim 27 wherein the length of thesubstrate comprises a roll of the substrate from which the selected areais removed.
 29. The method of claim 28 wherein the selected area is diecut from the roll of the substrate.
 30. A method of selecting an opticalpanel for a particular application comprising the steps of providing alength of substrate having a pattern of individual optical elements ofwell defined shape on or in the substrate that varies, the opticalelements being quite small in relation to a width and length of thesubstrate, selecting an area of the substrate that has a pattern of theoptical elements that best suits a particular application, and removingthe selected area from the substrate to provide the optical panel, theselected area having substantially less than a 100% of the total area ofthe pattern.
 31. The method of claim 30 wherein the pattern is arepeating pattern.
 32. The method of claim 30 wherein the pattern variesat different locations on the substrate.
 33. The method of claim 30wherein at least some of the optical elements have different shapes. 34.The method of claim 30 wherein at least some of the optical elementshave a different beam profile at different locations on the film. 35.The method of claim 30 wherein at least some of the optical elements arerandomly distributed on the film.
 36. The method of claim 30 wherein atleast some of the optical elements are oriented at different angles onthe film.
 37. The method of claim 30 wherein at least some of theoptical elements vary in at least one of the following characteristics:slope angle, density, position, orientation, height or depth, shape andsize.